The structure of the four‐component copolyester resulting from the exchange reaction between molten bisphenol‐A polycarbonate and poly(butylene terephthalate) is analyzed as a function of the reaction time by infrared and nuclear magnetic resonance spectroscopy. By applying a statistical method developed earlier, the mean chain length of the various sequences as well as the degree of randomness is computed. The exchange reaction leads initially to the formation of a block copolyester with reduced solubility. As the reaction proceeds, a soluble random copolycondensate is progressively formed.

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Suzuki cross-coupling reactions of 3-pyrroleboronic acid derivatives with haloaromatics and the reverse process i.e., the coupling of 3-iodo(bromo)pyrroles with arylboronic acids have been investigated as a potential key step in the synthesis of (-)-rhazinilam and analogues. It was found that 3-iodo-2-formyl-1-tosylpyrroles efficiently coupled with a variety of arylboronic acids in the presence of PdCl 2 (dppf) as catalyst. This catalytic system is compatible with a broad spectrum of arylboronic acids -electron-rich, electron-poor, hindered, heterocyclic -which easily coupled with the pyrrole substrate.Résumé : Nous avons étudié les réactions de couplage de Suzuki entre les acides 3-pyrroleboroniques et divers aromatiques halogénés ainsi que les réactions inverses de couplage entre les 3-iodo(bromo)-pyrroles avec des acides boroniques aromatiques. Cette réaction de couplage pourrait être une étape clé dans la synthèse du (-)-rhazinilame. Nous avons découvert que les 3-bromo-et 3-iodo-2-formyl-1-tosylpyrroles pouvaient être couplés efficacement avec un grand nombre d'acides boroniques en utilisant PdCl 2 (dppf) comme catalyseur. Ce catalyseur permet d'introduire facilement une grande diversité d'acides arylboroniques (riches ou pauvres en électrons, encombrés ou hétérocycliques) en position 3 du pyrrole.

AbstractÐSeveral RGD peptidomimetics have been prepared, in a convergent way, from the common ortho-aminotyrosine template (O-substituted with an anchorage-arm or a methyl group, and aN-substituted with a¯uorine tag for XPS analysis), and various o-aminoacid derivatives. The most¯exible compounds have shown a biological activity similar to that of the peptide reference (RGDS) in the platelet aggregation test. The compound 16a could be ®tted (by modelisation) with DMP 728 and c(RGDfV), two cyclic peptides that are good ligands of integrins. The compound 16b has been covalently ®xed on the surface of a poly(ethylene terephthalate) membrane used as support for mammalian cell cultivation. #

The pulsed magnetic resonance technique was applied to the measurement of the longitudinal (T1) and transversal (T2) relaxation time of water molecules adsorbed by Na‐ and Ca‐Montmorillonite, In the Na‐clay the water was adsorbed as a monomolecular layer whilst in the Ca‐clay, the bimolecular layer was formed under specified water vapor pressures. The effect of paramagnetic centers (Fe3+) was corrected and the samples were studied between + 30°C and −80°C. The main contribution to T1 was the “inter” contribution of protons diffusing from one water molecule to another whilst T2 results from simultaneous rotational (intramolecular) and diffusional (intermolecular) contributions. The proton diffusion coefficient and the life‐time of a proton on one specified water molecule is derived from T1 inter. The calculated value at 298°C is equal to 10−7 times the life‐time in liquid water, suggesting a dissociation degree 107 times higher in the adsorbed state than in liquid water. This increase in the dissociation degree as well as the reported activation energies are in good agreement with experimental data obtained from conductimetric and dielectric measurements performed previously.